The present disclosure relates to a method for drying a wet CO2 rich gas stream from an oxy-combustion process, in particular to a drying method with an adsorption process using a desiccant (adsorbent) and regenerating this adsorbent.
A wet CO2 rich gas stream from an oxy-combustion process has to be treated in order to remove H2O during or after a first compression step. The moisture of the wet CO2 rich gas stream has to be limited due to the need to avoid the formation of solid hydrates or a corrosive, free water phase during the downstream separation or injection process. For such a drying step or process, at least one vessel containing at least one desiccant for adsorbing the moisture from the wet CO2 rich gas stream passing the desiccant in one direction is typically used. For desiccant regeneration the flow through the desiccant bed is provided in the reverse direction. Typical installations foresee two dryers, where one is in operation whilst the other is in standby, respectively in regeneration mode.
Document WO 2009/071816 A2 discloses a method for drying a gas rich in carbon dioxide at high pressure, in which the gas rich in carbon dioxide is cleaned in an adsorption drying unit, comprising at least two bottles of adsorbent operating in a cycle in which one bottle is supplied with gas rich in carbon dioxide for drying whilst another bottle is pressurized and regenerated by means of a flow of dry gas produced by the drying unit, the drying unit producing at least one dry gas rich in carbon dioxide on the first pressurisation of at least one bottle, during which a pressurised gas other than a product from the drying unit is provided to the bottle.
It can be seen as disadvantageous from this known method that the produced dry gas rich in carbon dioxide is used as regeneration gas and after regeneration the gas is discharged to the atmosphere. This causes a disadvantageous loss of CO2. On the other hand recycling of the CO2 leads to disadvantageous increased power demand for compression.